If you’ve been trying to conceive without success, you’re not alone, and there are many possible explanations. About one-third of fertility problems trace back to the woman, one-third to the man, and the remaining third involve both partners or have no identifiable cause. Understanding the most common reasons can help you figure out what might be happening and what steps to take next.
How Long It Actually Takes
Before assuming something is wrong, it helps to know what “normal” looks like. A woman in her early to mid-20s has roughly a 25 to 30% chance of getting pregnant in any given cycle. That means even under ideal conditions, most months don’t result in pregnancy. By age 35, that probability has declined noticeably, and by 40, the chance per cycle drops to around 5%.
Doctors generally recommend seeking evaluation after 12 months of regular, unprotected sex if you’re under 35, and after 6 months if you’re 35 or older. These timelines aren’t arbitrary. They reflect how quickly fertility declines with age and how much time is reasonable to try before investigating further.
Your Fertile Window May Be Narrower Than You Think
Each cycle offers about six days when pregnancy is possible. Sperm can survive in the body for up to five days, and an egg lives only 12 to 24 hours after ovulation. That means you can conceive from sex that happens up to five days before ovulation or one day after, but outside that window, conception isn’t possible no matter how often you have sex. For the best odds, having sex every day or every other day during those six days is what the research supports.
If your cycles are irregular, pinpointing ovulation becomes harder. Ovulation predictor kits, basal body temperature tracking, and cervical mucus changes can all help you identify when that window opens. Missing it by even a couple of days each month can make it feel like something is wrong when the timing simply hasn’t lined up.
Ovulation Problems Are the Most Common Female Factor
Irregular or absent ovulation accounts for the majority of female infertility cases. If you’re not releasing an egg, there’s nothing for sperm to fertilize. Several conditions disrupt ovulation:
- Polycystic ovary syndrome (PCOS) is one of the most common culprits. It involves hormonal imbalances that prevent eggs from maturing and releasing on a regular schedule. Irregular periods, acne, and excess hair growth are typical signs.
- Primary ovarian insufficiency means the ovaries stop functioning normally before age 40, sometimes due to autoimmune conditions, genetics, or prior chemotherapy. The ovaries produce fewer eggs and less estrogen.
- Excess prolactin production from the pituitary gland can suppress estrogen and interfere with ovulation, sometimes without obvious symptoms beyond missed periods.
Blocked Fallopian Tubes and Uterine Issues
Even if you’re ovulating normally, the egg and sperm need a clear path to meet. Damaged or blocked fallopian tubes prevent sperm from reaching the egg or stop a fertilized egg from traveling to the uterus. Pelvic inflammatory disease, often caused by untreated chlamydia or gonorrhea, is a leading cause of tubal damage. Previous abdominal or pelvic surgery, including surgery for an ectopic pregnancy, can also cause scarring that blocks the tubes.
Inside the uterus, fibroids (benign growths) and polyps can interfere with implantation, though many women with fibroids do conceive without difficulty. Structural differences in the uterus that are present from birth, such as an unusually shaped uterine cavity, can make it harder to become or stay pregnant.
Endometriosis and Fertility
Endometriosis occurs when tissue similar to the uterine lining grows outside the uterus. This tissue can cause scarring that blocks the fallopian tubes and prevents the egg and sperm from meeting. It can also interfere with implantation of a fertilized egg. Beyond the physical scarring, endometriosis appears to affect fertility in less direct ways, including possible damage to sperm or eggs themselves. Painful periods, pain during sex, and heavy bleeding are common signs, but some women with endometriosis have no symptoms at all.
Male Factors Matter Just as Much
Because male factors contribute to roughly a third of infertility cases, it’s a mistake to assume the issue lies only with the woman. A semen analysis evaluates sperm count, movement (motility), and shape (morphology). In most semen samples, only around 4 to 10% of sperm meet strict quality standards, which is considered normal. But when sperm count is very low, movement is poor, or the percentage of normally shaped sperm drops further, conception becomes harder.
Hormonal imbalances in men can also reduce sperm production or cause sexual dysfunction. Conditions like varicoceles (enlarged veins in the scrotum), prior infections, and certain medications can all affect sperm quality. A semen analysis is a simple, early step that can either rule out or identify a male factor quickly.
Weight, Smoking, and Environmental Exposures
Body weight has a measurable effect on fertility. Higher BMI is linked to longer time to conception, greater likelihood of needing fertility treatment, and higher risk of miscarriage. This relationship works in both directions: being significantly underweight can also disrupt ovulation. Smoking increases the time it takes to conceive for both men and women, and there is weaker but still notable evidence that heavy alcohol intake plays a role as well.
Environmental chemicals are an underappreciated factor. Endocrine-disrupting chemicals, found in everyday products, can mimic or block reproductive hormones. BPA, commonly found in plastics and food packaging, has been shown to compromise embryo implantation and is associated with ovarian cysts. Phthalates, used to make plastics flexible, and flame retardants called PBDEs are also linked to reproductive problems. Even low-level lead exposure can alter reproductive hormones in women. In Denmark, women under 40 who worked in the plastics industry were more likely to have sought fertility assistance than women of the same age without that exposure. Reducing contact with these chemicals (choosing glass over plastic for food storage, avoiding heated plastic containers, checking labels for phthalate-free products) is a reasonable precaution.
Unexplained Infertility Is More Common Than You’d Expect
Up to 30% of couples experiencing infertility receive a diagnosis of “unexplained infertility” after standard testing. This means ovulation has been confirmed, at least one fallopian tube is open, and the semen analysis looks adequate. It’s a frustrating diagnosis because it doesn’t point to a clear fix, but it doesn’t mean nothing can be done. Treatments like ovulation-stimulating medications, intrauterine insemination, and in vitro fertilization are all used with varying success rates for couples in this category.
What Fertility Testing Looks Like
A basic fertility evaluation tests both partners. For men, the starting point is a semen analysis and sometimes blood tests to check reproductive hormone levels. For women, testing typically includes blood work to assess hormone levels related to ovulation and ovarian reserve, along with imaging to check whether the fallopian tubes are open and the uterus looks normal. This imaging is often done with a procedure that uses dye to outline the tubes on an X-ray.
These initial tests can identify or rule out the most common causes relatively quickly. If the results point to a specific issue, treatment can be targeted. If everything appears normal, your doctor will discuss options based on your age, how long you’ve been trying, and your preferences. The evaluation process itself is straightforward and typically completed within one or two menstrual cycles.